1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and devices and, more particularly, to mechanisms and techniques for dampening a motion of a part of a regulator.
2. Discussion of the Background
A blowout preventer (BOP) is a safety mechanism that is used at a wellhead of an oil or gas well. The BOP may be used for offshore drilling and also for land-based drilling. The BOP is configured to shut off the flow from the well when necessary. One such event may be the uncontrolled flow of gas, oil or other well fluids from an underground formation into the well. Such event is sometimes referred to as a “kick” or a “blowout” and may occur when formation pressure exceeds the pressure applied to it by the column of drilling fluid. This event is unforeseeable and if no measures are taken to control it, the well and/or the associated equipment may be damaged.
Another event that may damage the well and/or the associated equipment is a hurricane or an earthquake. Both of these natural phenomena may damage the integrity of the well and the associated equipment. For example, due to the high winds produced by a hurricane at the surface of the sea, the vessel or the rig that powers the undersea equipment may start to drift, requiring the disconnection of the power/communication cords or other elements that connect the well to the vessel or rig. Other events that may damage the integrity of the well and/or associated equipment are possible as would be appreciated by those skilled in the art.
Thus, the BOP may be installed on top of the wellhead to seal it in case that one of the above events threatens the integrity of the well. The BOP is conventionally implemented as a valve to prevent and/or control the release of pressure either in the annular space between the casing and the drill pipe or in the open hole (i.e., hole with no drill pipe) during drilling or completion operations.
FIG. 1 shows a well 10 that is drilled undersea. A wellhead 12 of the well 10 is fixed to the seabed 14. A BOP 16 is secured to the wellhead 12. The BOP may be a ram block BOP, a blind BOP, etc. Ram-type BOPS typically include a body and at least two oppositely disposed bonnets. The bonnets partially house a pair of ram blocks. The ram blocks may be closed or opened with pressurized hydraulic fluid to seal the well.
FIG. 1 shows, for clarity, the ram BOP 16 detached from the wellhead 12. However, the BOP 16 is attached to the wellhead 12 or other part of the well. A pipe (or tool) 18 is shown traversing the BOP 16 and entering the well 10. The BOP 16 may have two ram blocks 20 attached to corresponding rods 22. Rods 22 move integrally with the ram blocks 20 along directions A and B to close the well 10.
As shown in FIG. 2, the BOP 16 may include, besides the ram block 20 and the rod 22, an extension rod 24 that may be locked by a ram locking mechanism 26. An elastomer 28 is attached to the front side of the ram block 20 such that when the ram block 20 is closed and presses against the pipe 18, it ensures a substantial leakage free contact between the ram block 20 and the pipe 18, i.e., no liquid from below the ram block 20 escapes in the space above the ram block 20.
Extension rod 24 is connected to a piston 30 that is fitted inside an enclosure 32. Piston 30 splits the enclosure 32 into closed chamber 34 and opened chamber 36. FIG. 2 shows the closed chamber 34 having a maximum volume while the opened chamber 36 is squeezed to have a minimum volume and corresponds to a closed position of the ram block 20. When pressure is provided to the opened chamber 36 and the fluid in the closed chamber 34 is vented out, piston 30 moves to the left in FIG. 2, thus moving the ram block 20 to an open position.
The pressure to the opened chamber 36 and the closed chamber 34 is provided from, for example, accumulators 42, which are shown in FIG. 3. FIG. 3 shows a stack 40 of BOPS 16 disposed on top of each other and configured to be mounted with a flange 44 to a wellhead 12 (shown in FIG. 1). Stack 40 also includes, among other things, at least a regulator 46 for adjusting a pressure release by the accumulators 42 to conform to a required pressure for the opened and closed chambers. For example, such a regulator is configured to adjust an input pressure of 5,000 psi to an output pressure of 3,000 psi. As would be appreciated by those skilled in the art, such pressures are large and appropriate structures are provided to withstand such large pressures.
However, during testing of the BOP 16 for closing the ram blocks, when the pressure from accumulators 42 has been released, it has been observed that a component of the regulator 46, which adjusts the pressure and experiences linear motion inside the regulator, significantly oscillates (chatter), which leads to the failure of the regulator. It is observed that either this moving part or a part connected to this moving part fails during the oscillation regime.
The chatter is attributed to the ingress of air (or other fluid that is provided by the accumulator) in the piping of the regulator, which appears to cause excessive flow and instability. As the air compresses and expands, pressure waves are generated that react with the regulator and the regulator compensates those changes in pressure by adjusting a position of a moving part (slide) rapidly. The rapid movement of the regulator causes upstream pressure spikes, which may destroy the regulator slide in a matter of a few seconds in some cases.
Accordingly, it would be desirable to provide systems and methods that effectively overcome the above-noted exemplary problems.